ABSTRACT This K08 Mentored Career Development Award proposal describes a 4 year training program for the candidate, a neurosurgeon-scientist whose long term goal is to become an independent investigator in the field of primary malignant brain tumors, with a particular focus on the relevance of microRNA-mediated interference with GBM biology and survival response to conventional therapies. The basic science expertise earned by the candidate during his graduate studies while a resident in neurosurgery, put him in the ideal position to carry over this research. Previously, the candidate has shown that miR-128, a microRNA preferentially expressed in neurons, has an antitumor effect by targeting multiple GBM proteins involved with stem cell maintenance, as well as resistance to radiation therapy. He now hypothesizes that there are other microRNAs whose abnormal expression in GBM parallels that of miR-128, and thus that multiple microRNAs could work in functional clusters to effectively reprogram GBM cells into neuron-like cells by acting on a multiplicity of proteins with an epigenetic role. He also proposes that this can be harnessed to obtain a major sensitizing effect to radiation and chemotherapy. To test his hypothesis he proposes the following 3 specific aims: 1) to investigate the mechanistic and biological relevance of this observed clustering of several microRNAs in the regulation of multiple epigenetic complexes; 2) to design and construct a viral-based delivery method to re-express multiple microRNAs in GBM cells thus achieving substantial reprogramming of GBM cells into a more benign phenotype; 3) to explore how multiple microRNA re-expression can affect key cellular survival responses implicated in resistance to radiation and temozolomide treatment. This is extremely relevant because GBM is characterized by multiple aberrancies in several oncogenic pathways, which can not be targeted by single drugs, but could be regulated by these microRNAs clusters and their unique ability to simultaneously target multiple proteins fundamental to tumor biology. It is also very innovative, as it proposes a new approach to investigating the role of microRNAs in GBM, and also outlines a feasible method for producing artificial DNA sequences encoding multiple microRNAs that can be used in a gene-therapy setting. The candidate works in an exceptional academic environment, where he has already been able to set up his research laboratory, and will perform his experiments and proposed research under the guidance of Dr Chiocca and Dr Godlewsky as his co-mentors. Also, Dr Ligon, an expert in Neural and GBM stem cells and Dr Haas-Kogan, expert in DNA repair mechanism in brain tumors, will function as advisors for their respective areas of expertise. The candidate has already proven himself to be a dedicated and productive researcher, as demonstrated by his publications, awards, and funding, the last in chronological order being a K12 career development award obtained last year. To further advance his career development, the candidate has outlined his plan for specific hands-on training for mastering different research methodologies, such as comprehensive RNA and protein screening, interpretation of gene transcriptional analysis, and techniques for studying DNA damage and repair. In addition, the candidate will be involved in formal coursework in grant writing and responsible conduct of research.